Hey guys,  I wanted to know what would be a good dap to get. I currently have a Westone UM pro 30 with Ibasso DX50, but the soundstage isn't cutting it for me.  Was interested in either the sony ZX2 or the Hifiman HM901.  Im open to any other suggestions, and it needs to be  on amazon as I have...

Hi,  I've been doing a lot of research to find a decent headphone usb amp for my macbook air for my HD 598's.  I'm looking in the $100-200 range.     I've been looking at SMSL SD650, Yulong U100, JDS labs O2, Fiio E10K, Musical Fidelity V90 HPA, Firestone Audio Cute Curve, monoprice desktop...